DateTimeFormatter.parse returns an invalid Japanese date

Question

I'm trying to convert a Japanese date string to JapaneseDate.

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("Gyy年MM月dd日")
    .withChronology(JapaneseChronology.INSTANCE)
    .withResolverStyle(ResolverStyle.LENIENT);
JapaneseDate d = JapaneseDate.from(formatter.parse("平成01年01月01日"));
System.out.println(d);
System.out.println(d.format(formatter));

output:

Japanese Reiwa 71-01-01
令和71年01月01日

Since "令和元年" is "2019", "令和71年01月01日" is "2089-01-01". "平成01年01月01日" must be "1989-01-01".

How can I convert it correctly?

If I change the resolver style to ResolverStyle.STRICT, it throws

java.time.format.DateTimeParseException: Text '平成01年01月01日'
could not be parsed: year, month, and day not valid for Era

If I change the resolver style to ResolverStyle.SMART, it throws

java.time.format.DateTimeParseException: Text '平成01年01月01日'
could not be parsed: Invalid YearOfEra for Era: Heisei 101

Genni

Out of curiosity, what happens if you change to ResolverStyle.STRICT? – Tohubohu

@DavidConrad It throws java.time.format.DateTimeParseException: Text '平成01年01月01日' could not be parsed: year, month, and day not valid for Era. – Genni

@Abra I added Locale.JAPAN or Locale.JAPANESE to .ofPattern(). But nothing changes. – Genni

Answer 1

Try with this pattern:

DateTimeFormatter.ofPattern("Gy年MM月dd日")

---

y should be used single-handed otherwise it will be added a hundred years when it is up to 11 (cf. Javaバージョン別の改元(新元号)対応まとめ).

year 11:

JapaneseDate d = JapaneseDate.from(formatter.parse("平成11年11月01日"));

output:

Japanese Reiwa 81-11-01
令和81年11月01

year 12:

JapaneseDate d = JapaneseDate.from(formatter.parse("平成12年11月01日"));

output:

Japanese Heisei 12-11-01
平成12年11月01

Myrt